The lab I've used doesn't mount them. I get back a positive film strip that can be stored however I wish. All you can do is inquire at your lab. Typically slides in this format are being used to make color enlargements with, so mounting would hamper that.

I'm fairly sure you can get a projector for them; might be on the expensive side. Click on one of the store links here (B&H, et al); do a search in the store for possibilities.

I think typically they just come from the lab as a strip of film, but I do know there do exist mounts for different MF frame sizes; I remember seeing them last time I was at the B&H store in New York. They look just like 35mm mounts, but bigger. So I'm sure it's possible, but it just doesn't seem to be common practice.